Lotus’
Own Powerplant

Before
Lotus could embark on an ambitious new model programme it needed
a new engine, a fact realised as far back as 1964, just two years
after the twin-cam Lotus-Ford engine was launched.

A
further 24 months passed before it was decided that the new Lotus
powerplant would be a 150bhp, two-litre, four-valves per cylinder
design developed, under the guidance of Steve Sanville, head of
Lotus’ powertrain development. Lotus’ decision to go
ahead and produce its own engine — thereby freeing itself
of its dependence on Ford —coincided with Coventry Climax
withdrawal from motor racing allowing Chapman to quickly snap up
one of their leading engineers, Ron Burr, who had worked on the
four-valve-per-cylinder Coventry Climax FWMV racing engine and the
aborted flat-I 6 Fl engine.

Lotus
had given some thought to producing a BRM-designed 24-valve V6,
but this was discarded when it became apparent that a 120 degree
engine would have been too wide for the traditional Lotus chassis
and a 60 degree design too high for the low profile bonnets Chapman
envisaged. Lotus settled on a two-litre, 24-valve slant-four —
mounted at 45 degrees — which could be doubled up to a 4.2-litre
V8 for possible use at Indianapolis and as a road-going engine.
As the engine was intended for both road and competition, it embodied
the latest technology; aluminium block and head with removable wet
cylinder liners, twin belt-driven overhead camshafts, an oversquare
(95.25mm x 69.85mm) bore and stroke and a target output of 150Bhp.

At
the 1967 Earls Court Motor Show, Vauxhall unveiled its new slant-four
engine, whose bore centres were, remarkably, exactly the same as
those proposed by Lotus. Chapman immediately negotiated a deal with
Vauxhall — ironically owned by GM, who would later buy Group
Lotus —to buy some of their cast-iron blocks so that development
of Lotus’ own aluminium cylinder head could be speeded up.

By
1968 the first of these hybrid Type 904 engines — designated
by the marketing department as the LV220 for Lotus Vauxhall 220bhp
— fitted with Tecalemit-Jackson mechanical fuel injection
was up and running in the Lotus 62 sports-racing cars.

A
year later, now with Tony Rudd responsible for putting the engine
into production, prototype 147bhp Type 905s were put through reliability
trials in a Vauxhall Viva GT and a Bedford CF van. This was quickly
followed by the Type 906 which, effectively, put an end to the Lotus
Vauxhall hybrids.

The
development programme went through so smoothly that by 1970 the
engine was completed and ready for a car. Lotus invested £550,000
in machine tooling for the new engine and desperately needed to
recoup that money, but with its new model programme still someway
in the distance, and the Europa and Elan too small for the new power
unit, it would be nearly two years before the Type 907 engine appeared
in a production car and, even then, it wouldn’t be a Lotus.
When the BMC and Leyland empires merged under the leadership of
Sir Donald Stokes there were casualties, one of the most famous
being the big Austin-Healey 3000 sports car. Determined to continue
the Healey heritage Donald Healey and his son, Geoffrey, proposed
to Californian entrepreneur and former Healey dealer, Kjell Qvale
that they should team up and produce a new Healey sports car.

By
1968 the project was well underway and Hugo Pole penned a two-seater,
later modified by Bill Towns, based round Vauxhall Viva GT running
gear. Two years later Qvale bought the insolvent Jensen Motors,
made Donald Healey its chairman and told Jensen’s chief engineer,
Kevin Beattie, to get the Jensen-Healey into production. One of
the first snags they ran into was the Viva engine’s lack of
suitability caused by the increasingly stringent US exhaust regulations
which would have sapped the Vauxhall engine of any useful power.

Despite
the obvious Lotus Vauxhall link, it was Chapman who made the first
approach to Qvale offering 60 engines a week, well short of Jensen’s
200 cars a week production target. Undaunted at having been rejected,
Chapman approached Jensen a second time when it became obvious that
Lotus’ new GT wasn’t nearly ready. So it was that in
October, 1971 Jensen announced it would be taking up to 15,000 (!)
engines a year from Lotus.

In
Jensen trim, the 907 sported twin Dellortos — US cars had
horizontal Zenith Strombergs — and produced 140Bhp. The engines
weren’t without their problems due to oil collecting around
the valve gear so it didn’t drain back to the oil pump quickly
enough. The Lotus Elite eventually went into production in Spring
1974, powered by a 155bhp version of the 907, the extra power coming
from larger, 38mm choke, Dellorto carburetters. Those cars destined
for the USA had I 40bhp engines with a lower compression ratio —
8.4 against 9.5:1 — and twin Strombergs mounted on a water-heated
manifold.

Two
years of infield service resulted in a number of changes to the
907 in an effort to improve reliability, although Autocar still
thought the four-cylinder was “r6ugh at top end”. Motor
attributed the 907’s early problems to development work which
was carried out on sand-cast prototypes rather than die-cast production
units. Amongst the difficulties Jensen owners experienced with their
Lotus power-plants were distorted cylinder liners and pistons which
had a tendency to ‘pick up’, while Lotus improved engine
cooling by 10 degrees centigrade by fitting a skeleton-type toothed
belt guide at the front of the engine.

The
mid-seventies were turbulent times, not only in the UK with strikes
and a three-day week, but also in the Middle East where the after-effects
of the Arab-Israeli war of 1973 would have dire effects on the world’s
motor industry. Suddenly petrol was being restricted to the Western
nations by Arabian countries, who realised they had a means of holding
the West to ransom. (A mite simplified, granted.) Petrol prices
soared; Jensen collapsed in 1976. With it went Lotus’ engine
contract.

Things
were no better at Hethel, so there must have been a collective sigh
of relief when Chrysler UK contacted Lotus in 1978 about signing
an engine deal for a new rally car. At the time, Ford’s Escort
RS, with its 240-250bhp two-litre twin-cam, was the all-conquering
rally car and Des O’Dell, Chrysler’s competition director,
was determined to knock the RS off its pedestal. Although Chrysler
had an ideal car in the three-door Sunbeam hatchback, it lacked
an engine and indeed, the time, money and facilities to develop
one. It quickly dawned on O’Dell that the Lotus unit would
fit the bill nicely.

One
that never made it. Lotus helped Chrysler — later Talbot —
to develop a rally homologation special based on the Sunbeam three-door
with the new 2.2-litre engine crammed under the bonnet So successful
was this car that the brilliant young Finnish rally driver, Henri
Toivonen, won the 1980 RAC Rally in one and the following year the
Talbot factory team won the World Rally Championship for Makes.
Shades of Lotus Cortina development all over again. This is just
a publicity shot of an Essex-painted Sunbeam-Lotus. (Focalpoint)
A rally-tuned Lotus engine and five-speed ZF gearbox were engineered
into a prototype Sunbeam which, after some tuning and testing, went
on to gain second place in that year’s Mille Piste rally with
Tony Pond at the wheel. Encouraged by this result Chrysler gave
the go-ahead for 400 Sunbeam-Lotuses to be built for homologation.
However, the dealers had different ideas and such was their collective
enthusiasm that plans were laid to build 4500.

Prior
to the car’s launch in March 1979, Chrysler had sold its ailing
UK operation to the French Peugeot-Citroen group so the new rally
weapon was rechristened Talbot Sunbeam-Lotus.

Happy
as he was with the engine’s performance, O’Dell demanded
more torque and persuaded Lotus to take the engine capacity out
to 2.2 litres by increasing the stroke to 76.2mm. Concerned that
this would set up bad vibrations, Tony Rudd developed a flexible
flywheel which dampened out the problem and allowed the engine —
re-designated Type 911— to produce 150bhp at 5,750rpm and
ISO lbs/ft torque at 4,500rpm. In rallying trim the 2.2 produced
250bhp, sufficient for Henri Toivonen to win the 1980 RAC Rally
with team mates Guy Frequelin and Russel Brookes third and fourth,
respectively. But this was just a prelude of things to come: in
the following year works Sunbeam-Lotus won the Argentine Rally and
came second on the Monte Carlo, Portugal, Corsica, Brazil and San
Remo events, sufficient for them to win the prestigious Championship
of Makes and for Frequelin to finish as runner-up in the Drivers,
series.

All
2.2 litre Lotus engines are assembled on site at Hethel

Despite
all this success only 2,298 Sunbeam-Lotus were sold between 1979
and 1981, half the number originally envisaged. The Type 912 2.2-litre
Lotus used in its own cars from 1980 onwards differs from the rallying
version in having, amongst other things, a redesigned sump and main
bearing panel; it also produced 160bhp at 6,500rpm and 160 lbs/ft
torque at 5,000rpm.

If
there is one engine that means ‘Lotus’ as much as an
air-cooled flat six is a ‘Porsche’, it’s the Type
910 turbo, nowadays the only engine Hethel builds. The Esprit with
its aggressive Giugiaro styling always deserved more than 160bhp
and while many at Lotus fought for the Type 908 four-litre V8, this
project was abandoned after a Lotus Engineering client pulled out
of a deal to buy sufficient engines to make manufacturing economically
viable. Turbo-charging, which was rapidly becoming fashionable in
1980, seemed the way to go, but only if Lotus could conquer the
dreaded turbo-lag problem which cursed blown engines at that time.

The
Type 910 isn’t just a normally-aspirated engine with a turbo
bolted on the side, it is a fully re-engineered power unit that
has been progressively developed into one of the world’s great
turbo-charged engines.

Throughout
its life, the Excel’s engine remained carburetted. There was
much talk of fuel-injection, but it was felt that too much development
time would have to be spent on then updating the chassis and interior
to warrant the expenditure. Anyway, a 2+2 version of the Elan was
envisaged to take over from the Excel. (I Adcock, Car courtesy of
London Lotus Centre)

Although
based on the 2.2-litre 907 there are a number of significant changes:
lowering the compression ratio to 7.5:1 from 9.5:1 was a major step
towards improved throttle response, but also entailed designing
new forged pistons while new camshaft profiles opened the valves
further and longer. Inlet valves were sodium filled, the valve seats
hardened, cylinder head water passages enlarged and a bigger water
pump installed to help reduce temperatures. The integrated main
bearing panel was also strengthened and to ensure there was adequate
oil supply a dry sump system with a separate oil tank, an additional
scavenge pump and an oil-cooler installed. (This system lasted until
March 1983, when the Turbo Esprit inherited the radial sump baffle
system originally designed for the stillborn V8).

A
single Garret AiResearch T3 turbo supplied eight pounds of boost
to the pressurised Dellorto 40 DHLA twin-venturi side draught carburettors.
Never ones to conform, the Lotus turbo system blew rather than sucked
air through the carburettors which meant special seals for the throttle
spindles to prevent the petrol/air mixture escaping.

Unconventional
the Turbo Esprit’s powerplant might have been, but you couldn’t
argue about its effectiveness: 210bhp at 6,500rpm and 200 lbs/ft
torque at 4,250rpm, enough to slingshot Motor’s road testers
from 0-60mph in 5.6 secs and on to a 140+mph maximum, though the
latter was somewhat down on Lotus’ optimistically-claimed
150+ top speed. The turbo engine remained unchanged until early
1987 when the HC version debuted with its compression raised to
8.0:1 and boost increased to 9.5 psi. Those changes — together
with bigger Dellorto 45M DHLA carburettors, a smaller turbine for
better low-speed response, a balance pipe for more even mixture
distribution, enlarged exhaust and inlet valve passages and more
efficient oil and water cooling systems — added a further
5bhp at 6,000rpm and, more significantly, an additional 20 lbs of
torque at the same 4,250rpm engine speed. On the test track this
lopped a fifth of a second off Motor’s 0-60mph time, though
the HC’s maximum speed was still 6mph shy of the magic ISO.

The
still controversial DeLorean DMCI 2; the rear-engined, gull-winged
coupe which Lotus spent two years developing for John DeLorean between
1978 and 1980. Production lasted from December 1980 through to October
1982 when the receivers were called in. More than a decade later,
the financial shenanigans involving DeLorean, Cohn Chapman and Fred
Bushell (Chapman’s right-hand man ever since the days at Hornsey),
and others has never been satisfactorily resolved
For 1987 Lotus concentrated on developing the car’s looks
and handling rather than its performance, nevertheless the blown
four got a watercooled turbocharger and an integral, rather than
separate, wastegate although neither improvements affected the bhp
and torque delivered. The normally-aspirated engine — Type
91 2S — also got a power hike to 172bhp and 163 lbs/ft thanks
to a 10.9:1 compression ratio and a pair of Dellorto DHLA 45 D carbs.

At
this time the search for ultimate power didn’t force the pace
of Lotus’ engine development, but rather a determination to
maintain power outputs in the face of increasingly stringent emission
and fuel consumption regulations from the USA, which was becoming
a vital market for Lotus sales.

GM’S
takeover of Lotus in 1986 gave the engineers at Hethel access to
possibly the world’s largest parts bin — suddenly there
was scope to purchase and use sophisticated engine management systems
and the like at attractive prices. In the past Lotus’ small
production numbers meant that original equipment suppliers were
reluctant to provide Lotus with the components at realistic costs.

To
meet the US ‘Federal’ regulations the Esprit Turbo had
to go fuel-injected and, thanks to a multi-point system from GM
subsidiary, AC Delco, Lotus were able to meet the exhaust and fuel
consumption regulations at a lower cost than the previously used
Bosch K-Jetronic system.

Ironically,
the US-specification cars produced more power — 228bhp at
6,000rpm — and torque, 218 lbs/ft at 4,000rpm, than either
European or UK cars. Although both markets eventually inherited
this system when the non-turbo, carburetted, Esprit was discontinued
from the model lineup. Using an advanced MPFI and engine management
system opened up tremendous possibilities for Hethel’s engine
boffins — the pursuit of raw power for power’s sake
was now on.

In May, 1989 the Esprit Turbo SE debuted with some startling figures:
264bhp at 6,500rpm, 261 lbs/ft at 3,900rpm, 0-60mph in 4.7 secs,
0-100mph in I 1.9 secs and a 164mph maximum speed. The Esprit had
become a true supercar.

These
figures weren’t generated by a new engine, but a highly refined
and developed version of the venerable 2.2-litre straight-four,
making it the most powerful 16-valve engine in the world at 121.5bhp
per litre. The only major internal change to the engine were Mahle-forged
pistons with chrome-plated crowns running at an 8.0:1 compression
ratio, although items like the induction system and the (catalysed)
exhaust were updated. The massive power increase was mainly due
to a sophisticated MPFI system and a charge-cooler.

The
MPFI system was controlled by a fully adaptive Delco Electronics
ECM which ‘learnt’ the precise engine demands for each
journey, according to ambient temperatures, engine loads, fuel used
etc. as well as controlling the quartet of Multec fuel injectors.
The injectors normally pulsed once every engine revolution, with
half the fuel requirement for each cylinder’s combustion being
supplied by each pulse (‘alternating double fire’).
At very low injection rates the system automatically changed to
alternating single fire to maintain a minimum injection period for
accurate fuel flow. At very high engine loads additional fuel flow
was provided by two secondary injectors positioned in the plenum
nozzle.

A
liquid-cooled charge air-cooler was selected to reduce the turbo-charged
air temperature and, to put it simply, ram more into the combustion
chambers. The engine-mounted charge-cooler connected the turbo compressor
directly with the plenum nozzle. Consisting of a series of liquid
and air passages with internal finning, the cooling liquid was circulated
through the cooler by a pump driven off the distributor shaft and
thence to a front-mounted radiator. This system was independent
of the engine’s own coolant network.

The
conventional coil and distributor were replaced by a direct ignition
system with two separate ignition coils, while a block-mounted knock
sensor retarded the spark if detonation occurred. If the detonation
continued for more than two seconds then boost pressure was automatically
reduced.

Under
normal circumstances the Garrett TBO3 turbo blew at 12.4psi, but
during hard acceleration below 3,000rpm over boost cut in for up
to 30 seconds for even more rapid progression. The new Esprit duly
stunned the motoring press. Richard Bremner wrote in Car; “In
the roll-call of supercars, the Lotus Esprit Turbo can suddenly
stand proud. It now has the horsepower and performance not merely
to stand comparison with Porsche 91 I s and Ferrari 328s, but to
embarrass them, too’~

For
MY ‘91 Lotus went all-turbo, dropping the normally-aspirated
base Esprit from the UK lineup. The mid-range turbo was, in fact,
the fuel-injected 2,28bhp model that the Americans and Europeans
had enjoyed for some time. Following the introduction of the charge-cooled
Esprit, Lotus undertook a racing programme in the American SCCA
World Challenge Series for sports cars. In addition to the lighter
bodyshell, the competition SE’S engine power was further increased
to 300bhp thanks to a reworked cylinder head, a larger Garrett T4
turbo, larger injectors, a recalibrated engine management system
and a bigger charge-cooling system created by integrating it with
the redundant air-conditioning radiator. The power increase was
impressive: 300bhp at 600rpm, an estimated 261 lbs/ft at 3,900rpm,
a claimed 168mph max and 0-60mph in 4.4secs.

How
much more power can Lotus extract from its venerable 2.2-litre engine?
In Sport 300 guise a re-worked cylinder-head, hybrid turbocharger,
an enlarged chargecooler and revised engine management system pushed
out put up to 300bhp giving the car a 167mph top speed. (Focalpoint)
Eventually this engine found its way into the limited edition Sport
300 which appeared at the 1992 Birmingham Motor Show. Despite the
engine’s advanced years and growing press criticism —
“the Esprit’s snarling slant-four sounds hard-edged
and coarse, even metallic when idling” (Roger Bell in Car)
— Lotus reaffirmed its faith in the 22 year-old engine when,
in early 1993, they revealed the Esprit S4, simultaneously announcing
that the 264bhp engine benefited from all new castings for the block,
head and sump for increased stiffness and cooling capacity. The
Turbo’s engine management system was also re-mapped for improved
response and driveability, although power and performance figures
remained unchanged over the original charge-cooled Esprit. A two-litre,
tax-breaking version producing 186bhp was also built for the Italian,
Greek and Portuguese markets.

As
the years slip by and more rival sports car producers abandon the
turbo concept in preference to six- or eight-cylinder normally-aspirated
engines, it is difficult to see just how Lotus can maintain its
present position with a small-capacity four which, for all its sophistication,
has to work very hard for a living. Perhaps Lotus will have to turn
to a major supplier for its next engine block and develop their
own heads etc. If that transpires then the circle will have been
completed, but en route will be the legacy of a truly fine engine
that became a benchmark for prodigious specific output from a small
capacity.